The Government is drawing up plans to sell off publicly owned forests in a move that could see private developers allowed to clear ancient trees to make way for holiday resorts, golf courses and adventure playgrounds.

The plan is designed to raise funds to help to pay off the Budget deficit, but has been met by opposition from some of Britain's highest-profile nature lovers.

The Department for Environment, Food and Rural Affairs plans to dispose of about half the land looked after by the Forestry Commission, raising fears that the trees will disappear to be replaced by amusement parks and other ventures. The Forestry Commission holds about 1.85 million acres of woodland, about a third of which may be sold off, in one the biggest land sales in British history.

Laws governing the forests date back to Magna Carta in 1215 and they may have to be changed to facilitate the sale. One hope of protecting the forests lies in their purchase by nature charities or private benefactors such as the publisher Felix Dennis, who has planted the "Forest of Dennis" in Warwickshire, and the financier Ben Goldsmith, who has funded projects to prevent the disappearance of forests through a foundation named after his father, Jimmy.

Yesterday Mr Goldsmith gave warning that a quick sale could mean that the forests are bought too cheaply.

"The observation I would make is that Great Britain is miles behind any other country in Europe in making use of its forest resources," he said. "Everywhere else in Europe has lots of small biomass-generation plants. We don't have that network, which makes me question whether it's the best time to be selling our forests.

"As an environmentalist, I very much hope they won't think of selling off the biggest and best of our forests, like the Forest of Dean," he added. "I hope that remains in public hands." There are a small number of wealthy nature lovers in Britain with a track record for using their private wealth to preserve forest land. One of the best known is the millionaire philanthropist Mr Dennis, who was jailed 30 years ago for his part in producing the hippie magazine, Oz, which was judged obscene, but went on to have a successful business career. He has covered about 1,000 acres of countryside with 600,000 saplings.

The Tory MP Zac Goldsmith, who headed David Cameron's task force on the environment when the Conservatives were in opposition, said last night: "There are patches of Forestry Commission land that I would not object to the Government selling, as long as the forests are properly maintained. I have no objection to some uses of the forests, like coppice and biomass production, which can improve biodiversity and provide jobs. But if forests are simply sold off to developers, that should and would not be accepted. There are great national forests, for example the New Forest, that need maximum protection by Government."